抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://www.cell.com/cell/pdf/S0092-8674(09)01243-4.pdf

Cellular and Molecular Mechanisms of Pain

Degeneration and regeneration of the nervous system

Dipstick and lateral-flow formats have dominated rapid diagnostics over the last three decades. These formats gained popularity in the consumer markets due to their compactness, portability and facile interpretation without external instrumentation. However, lack of quantitation in measurements has challenged the demand of existing assay formats in consumer markets. Recently, paper-based microfluidics has emerged as a multiplexable point-of-care platform which might transcend the capabilities of existing assays in resource-limited settings. However, paper-based microfluidics can enable fluid handling and quantitative analysis for potential applications in healthcare, veterinary medicine, environmental monitoring and food safety. Currently, in its early development stages, paper-based microfluidics is considered a low-cost, lightweight, and disposable technology. The aim of this review is to discuss: (1) fabrication of paper-based microfluidic devices, (2) functionalisation of microfluidic components to increase the capabilities and the performance, (3) introduction of existing detection techniques to the paper platform and (4) exploration of extracting quantitative readouts via handheld devices and camera phones. Additionally, this review includes challenges to scaling up, commercialisation and regulatory issues. The factors which limit paper-based microfluidic devices to become real world products and future directions are also identified.

Paper-based microfluidic point-of-care diagnostic devices

Coronavirus disease (COVID-19) is a pandemic disease, which has already caused thousands of causalities and infected several millions of people worldwide. Any technological tool enabling rapid screening of the COVID-19 infection with high accuracy can be crucially helpful to the healthcare professionals. The main clinical tool currently in use for the diagnosis of COVID-19 is the Reverse transcription polymerase chain reaction (RT-PCR), which is expensive, less-sensitive and requires specialized medical personnel. X-ray imaging is an easily accessible tool that can be an excellent alternative in the COVID-19 diagnosis. This research was taken to investigate the utility of artificial intelligence (AI) in the rapid and accurate detection of COVID-19 from chest X-ray images. The aim of this paper is to propose a robust technique for automatic detection of COVID-19 pneumonia from digital chest X-ray images applying pre-trained deep-learning algorithms while maximizing the detection accuracy. A public database was created by the authors combining several public databases and also by collecting images from recently published articles. The database contains a mixture of 423 COVID-19, 1485 viral pneumonia, and 1579 normal chest X-ray images. Transfer learning technique was used with the help of image augmentation to train and validate several pre-trained deep Convolutional Neural Networks (CNNs). The networks were trained to classify two different schemes: i) normal and COVID-19 pneumonia; ii) normal, viral and COVID-19 pneumonia with and without image augmentation. The classification accuracy, precision, sensitivity, and specificity for both the schemes were 99.7%, 99.7%, 99.7% and 99.55% and 97.9%, 97.95%, 97.9%, and 98.8%, respectively. The high accuracy of this computer-aided diagnostic tool can significantly improve the speed and accuracy of COVID-19 diagnosis. This would be extremely useful in this pandemic where disease burden and need for preventive measures are at odds with available resources.

Can AI Help in Screening Viral and COVID-19 Pneumonia?

This paper describes enzyme-linked immunosorbent assays (ELISA) performed in a 96-microzone plate fabricated in paper (paper-based ELISA, or P-ELISA). ELISA is widely used in biochemical analyses; these assays are typically carried out in microtiter plates or small vials. 2] ELISA combines the specificity of antibodies with high-turnover catalysis by enzymes to provide specificity and sensitivity. We have recently described a 96-microzone paper plate— fabricated by patterning hydrophobic polymer in hydrophilic paper—as a platform for biochemical analysis. Although microfluidic paper-based analytical devices (mPADs) were designed primarily to provide analytical capability at low cost in developing countries, we expect that they will also be useful in applications such as point-of-care clinical analysis, military and humanitarian aid field operations, and others where high throughput, low volumes of sample, low cost, and robustness are important. These devices have so far been prototyped using analyses of simple analytes: glucose, total protein, and certain enzymes. P-ELISA combines the sensitivity and specificity of ELISA with the convenience, low cost and ease-of-use of paper-based platforms; P-ELISA (at it current state of development) is faster and less expensive than conventional ELISA, but somewhat less sensitive. Porous membranes, including nitrocellulose and filter paper, have been used for decades in dot-immunobinding assays (DIA). Though DIAs are the simplest form of immunoassays on paper, they typically require one piece of nitrocellulose for each assay; the pieces of nitrocellulose have to be processed individually in Petri dishes, and the assays take several hours to complete. Quantitative DIAs have been reported, but DIAs are typically qualitative, and provide only “yes/no” results. Conventional ELISA, usually performed in 96-well plates (fabricated by injection molding in plastic), is quantitative and well-suited for highthroughput assays, but each assay requires large volumes (ca. 20–200 mL) of analyte and reagents, the time required for incubation and blocking steps are long ( 1 h per step, because the reagents must diffuse to the surface of the wells), and the results are usually quantified using a plate reader, typically a $20 000 instrument. Paper microzone plates for ELISA can have the same layout as plastic 96-well plates, but each test zone requires only about 3 mL of sample, and the results can be measured using a desktop scanner, typically a $100 instrument. In addition, an entire P-ELISA can be completed in less than one hour. The ease of fabrication of paper microzone plates also opens opportunities for a wide range of non-standard formats, and customized connections to carry reagents between zones. To evaluate the feasibility of P-ELISA, and the potential advantages and disadvantages of P-ELISA and 96-well-plate-based ELISA, we adapted a standard procedure to our format and then demonstrated an indirect P-ELISA using rabbit IgG as a model analyte. We also established that P-ELISA can be used to detect and quantify antibodies to the HIV-1 envelope antigen gp41 in human serum using an anti-human IgG antibody conjugated to alkaline phosphatase (ALP) to produce a colorimetric readout. We used a 96-microzone paper plate with an array (12 8) of circular test zones for running multiple P-ELISAs in parallel (Figure 1A); the Supporting Information describes the details. The array was designed to have the same layout and dimensions as a standard plastic 96-well plate, so that it would be compatible with existing microanalytical infrastructure (eightor twelve-channel pipettes and plate readers). Each test zone was 5 mm in diameter and required 3 mL of solution to fill (e.g., to wet completely with fluid); this design was a good compromise between convenience and conservation of reagents, as it reduced the amount of reagents and sample required for the assay but ensured accurate distribution of fluids when using a manual pipette. We also examined smaller test zones, with the smallest test zone requiring 0.5 mL of solution to fill (e.g., to wet completely). This size is similar to that required in a 384-well plate format. The top and bottom faces of the test zones in papermicrozone plates are open to atmosphere. The advantage of this configuration is that the zones can be washed by adding a washing buffer to the top of the zone while pressing the bottom of the zone against a piece of blotting paper. The washing buffer goes through the test zone vertically and into [*] Dr. C.-M. Cheng, Dr. A. W. Martinez, Dr. J. Gong, Dr. C. R. Mace, Prof. S. T. Phillips, Prof. E. Carrilho, K. A. Mirica, Prof. G. M. Whitesides Department of Chemistry and Chemical Biology Harvard University Cambridge, MA 02138 (USA) E-mail: gwhitesides@gmwgroup.harvard.edu Homepage: http://gmwgroup.harvard.edu

Paper-Based ELISA

This paper describes three-dimensional microfluidic paper-based analytical devices (3-D µPADs) that can be programmed (postfabrication) by the user to generate multiple patterns of flow through them. These devices are programmed by pressing single-use ‘on’ buttons, using a stylus or a ballpoint pen. Pressing a button closes a small space (gap) between two vertically aligned microfluidic channels, and allows fluids to wick from one channel to the other. These devices are simple to fabricate, and are made entirely out of paper and double-sided adhesive tape. Programmable devices expand the capabilities of µPADs and provide a simple method for controlling the movement of fluids in paper-based channels. They are the conceptual equivalent of field-programmable gate arrays (FPGAs) widely used in electronics.

/pdf/programmable-diagnostic-devices-made-from-paper-and-tape-1fm73dzdbr.pdf

Programmable diagnostic devices made from paper and tape

Biofilms in Chronic Wounds: Pathogenesis and Diagnosis

The use of inexpensive materials and cost-effective manufacturing processes for mass production of microfluidic devices is very attractive and has spurred a variety of approaches. Such devices are particularly suited for diagnostic applications in limited resource settings. This review describes the recent and remarkable advances in the use of low-cost substrates for the development of microfluidic devices for diagnostics and clinical assays. Thus, a plethora of new and improved fabrication methods, designs, capabilities, detections, and applications of microfluidic devices fabricated with paper, plastic, and threads are covered.

Recent advances in low-cost microfluidic platforms for diagnostic applications.

At the end of 2019, the novel coronavirus disease (COVID-19), a fast-spreading respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was reported in Wuhan, China and has now affected over 123 countries globally [...].

https://www.mdpi.com/2075-4418/10/3/165/pdf

Chao-Min Cheng

Papers

Paper-Based ELISA

Programmable diagnostic devices made from paper and tape

Biofilms in Chronic Wounds: Pathogenesis and Diagnosis

Recent advances in low-cost microfluidic platforms for diagnostic applications.

Point-of-Care RNA-Based Diagnostic Device for COVID-19.